Radiotelegraph signaling system



www-E d., as, 393% H. PRATT ETl AL RADIO TELEGRAPH SIGNALINQ SYSTEM 5SheetsSheet 1 Fiied Jan. 3. 1921 /M/iwb EN P WITNESS afa-u'. ATTORNEYSm., le, ma. A LME-sw H.PRATT ET AL RADIO TELEGRAPH SIGNALING 4SYSTEMFiled Jan s. 1921 s sheets-snaai 2 ILHI f-/glllfg/J-lL-U.

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WITNESS ci. 16, i923.

H. PRATT ET M.

RADIO TELEGRAPH SIGNALING SYSTEM Filed aan; '3. 1,921 s sheets-sheet 3lliL /l Z/ WITNESS l I .INVENTORS H ade Pratt Hrfg @nab BY A Patentedst. 16, 1923.

HARADEN PRATT, OF SAN FRANCISCO, HAROLD F. ELLIOTT, OF PALO ALTO, EU-GENE B. MURPHY, OF BURLINGAME, CALIFORNIA, ASSIGNORS TO AUGUSTUS TAY-LOR, OF SAN FRANCISCO, CALIFORNIA.

RADIOTELEGRAPH SIGNALING SYSTEM.

Application led January 3, 1921. Serial No. 434,420. i

T 0 all whom t may concern Be it known that We, I-IARADEN PRATr, HAROLDF. ELLio'rr, and EUGENE B. MUR- PHY, citizens of the United States,residing,

respectively, in the city and county of San Francisco, Palo Alto, SantaClara County, and Burlingame, San Mateo County, all in the State ofCalifornia, have invented cer,- tain new and useful Radiotelegi'aphSignaling Systems, -of which the following is a specification.

'Ihe invention relates to a radio telegraph signaling system in whichaudio frequency Wave trains are radiated from an antenna system to Whichan undamped Wave arc generator is connected.

It is desirable for several reasons, under certain conditions, to,produce laudio frequency Wave trains from a continuous undamped Wavetransmission system and several methods have been suggested foraccomplishing such result. In these methods the continuous Wave has beenbroken up into time spaced groups at such a frequency that the groupfrequency is Within the range of audibility. This has been accomplishedby interrupting the antenna circuit at an audio frequency rateand-'shunting the arc .with a condenser circuit or an oscillatorycircuit, into which the radio frequency current passed during theinterval that the antenna circuit was opened, or during the time thatits resistance was largely increased. TheseA methods all involve thecontinuous and normal operation of the arc, and during the intervalsofno radiation the energy of the arc is Wasted in the shunt oroscillatorycircuit.

An object of our invention is to produce modulation of the antennacurrent at audio frequencies, in an arc radio transmitter.

Another object of Vour invention is to eliminate a certain Waste ofenergy in performing such modulation for producinga more economicallyoperating system.

The invention possesses other advantageous features, some of which, withthe foregoing, vvill be set forth at length in the followingdescription, Where We shall outline in full the method of our inventionand several forms of systems 'for putting it into practice, whichsystems are shown in the drawingsaccompanying and forming part of thepresent specification.l In said draw-- ings, We have shown severalsystems for carrying out our invention, but it is to be understood thatwe do notlimit ourselves to such systems, since the method, as ex ressedin the claims, may be embodied in ot er systems.

Referring to such drawings: Figures 1 to 11- inclusive, are diagrammaticrepresentations of different forms of the system of our invention. Inaccordance with our invention, We provide for the audio frequencymodulation of an arc generated radio frequency current, by extinguishingand reignitingsthe arc flame at an audio frequency rate, by suitablemeans such as an oscillatory circuit resistance control. Byextinguishing and reigniting the arc at audio frequency, groups ofundamped Waves are radiated from the antenna, the groups being emittedat audio frequency. During the time that thearc is extinguished, thereis very -little energy consumption, so that a gain in eiiiciency ofoperation is obtained.

We have found that it is a fundamental characteristic of the arc, thatis, the Poulsen arc, When used as a converter of energy for producingradio frequency currents, that thearc length must increase When theresistance of the oscillatory circuit is increased, if oscillations areto be maintained. Inorder to maintain a longer arc, it is necessary tosupply a higher direct current voltage, and, if this is not-done, thearc is immediately extinguished, due to the action of the transversemagnetic field. The voltage of the-direct current generator beingmaintained substantially constant, When the resistance of theoscillatory circuit 1s in-4 creased, the arc is instantaneouslyextinguished.

quickly Withdrawn, the extinguished arc- Will immediately reignite, dueto the presllO 9.5 We have further found that if the oscil- I' latorycircuit resistance is inserted and then tenna circuit at an audio freuency rate, with extinction and ignition of tlhe arc flame atI the samerate, producing an antenna current with corresponding amplitudefluctuations, producing thus suitable wave trains. ln accordance withour invention, we increase and decrease the resistance of theantennacircuit at audio frequency, thereby interrupting and reignitingthe arc at such 'frequency and produce audio frequency wave groups inthe antenna circuit.

ln the drawings we have shown several different circuits embodying thesystem of our invention. Each circuit includes a Poulsen arc generator,comprising'an arc 2 enclosed in an atmosphere containing hydrogen, andsubjected to a strong transverse magnetic field produced by theelectromagnets 3, which are energized by direct current from thegenerator l. One side of the arc is grounded and the other side isconnected 'to the antenna 5, through the variable inductance 6. Mea-nsare provided for introducing into and withdrawing from the antennacircuit, at audio frequency, resistance suiiicient to extinguish the arcwhen introduced into the circuit. In the system shown in Fig. 1,theresista-nce 7 is arranged in the antenna circuit and shunted around theresistance is a low-resistance circuit containing a rotary.I motordriven commutator 8, having alternate insulating segments and commutatorsegments.. rllhe commutator is engagedby brushes having a suitablewidth. 'lhe rotatingv commutator periodically shortcircuits theresistance 7, so that the resistance is alternately effectively placedinto and removed from the circuit. The commutator is rotated at suchspeed that the arc is interrupted at audio frequency.

ln the system shown in Fig. 2. the resistance 9 is arranged in thecommutator circuit which is arranged in parallel with a portion of theoscillatory circuit inductance 6 which is equivalent to introducing theresistance directlyv in series in the oscillatory circuit.

The system shown in Fig. 3 is similar to -that shown in Fig. 2, with theexception that the commutator-resistanc circuit is coupled to theoscillatory circuit br an air-core transformer 12. lin the system shownin Fig. 4r,

lan iron core transformer 13 is employed in place of the air coretransformer.

rlhe system shown in Fig. 5 is similar to that shown in Fig. 2, with theexception that the c'ommutator circuit is connected around a condenser14, instead of around la, portion of the inductance 6.

'lhe s stems shown in Figs. 6, 7, 8 and 9 are mo iications of thelsystems shown in Figs. 2, 3, t and 5 respectively, in which a rotaryspark gap device 15 ,is substituted for f the-commutator 8. When thespark gap electrodes come into alinement, the potential in the circuitcauses a spark dischargei thereinviare by closing the circuit throughthe resistance,

' which has the equivalent eect of inserting ,l the resistance in theoscillatory circuit.

ln Fig. 10, we have shown a system showin the application of this methodof signa ing-to coupled circuits. 'lhe arc 2 is contained in a closedcircuit containing the ca-y pacity 25 rand the transformer primary 26,which is coupled to the secondary 27 in the antenna circuit. rllheinterrupter 28 is associated With the circuit to which the arc converteris connected in the present instance, the interrupter bein arranged toshunt a resistance 29 in the circuit.

The circuits shown in Figs. d and 8, iny volving the use of the ironcore transformer coupling, will only lwork properly when there are fewlosses in the iron core, which condition-it is often. difficult torealize in practice. 'lhe system shown in Fig. 11 will give satisfactoryoperation with an iron core transformer having substantial losses. lnthis .system the resistance 31Vis permanently connected across thesecondary of the iron core transformer 32 and .the interrupter 33 isconnected across the resistance, so that it operates to short circuitthe resistance.

lt is to be understood that-in the above circuits the rotary commutatorsand spark gaps are so designed as to cause connections or sparks to bemade at any convenient audio frequency rate. The times of contact makingor sparking which are determined by the relative widths 'of the metallicand insulated commutator segments, or by the relative widths of theelectrodes and spaces on the rotary gap disc, constitute a feature ofthis invention as best results are obtained when a definite ratio inthese times is selected.

llt is to be further understood that the resistances and transformerratios are so selected in each of the above examples that the equivalentresistances, respectively, of the oscillatory circuits, will be as greator greater than the amount required for complete arc extinguishment.'lhese quantities may be easilydetermined by calculation, or by trial.

'llhe circuit constants are further so arranged that a low voltage isutilized with the commutator connection so that sparking at the brushesof the latter may be a minimum, and a high voltage with the spark gap sothat the discharges across the latter may be uniform and regular.

Signaling may be accomplished in any suitable manner, and in thedrawings we have shown one form of signaling circuit which isparticularly a plicable to the systemof this invention. @onnected aroundthe arc is a circuit 16 containing a resistance and the normally closedsignaling key 22. When the circuit 16 is open, radio frequency currentis delivered to the antenna and when the circuit 16 is closed, theresistance 17 short-circuits the arc, thereby extinguishing it entirely.The contacts of the relay key 18 may be placed Within the arc chamber ina position which causes the spark produced by their opening, to reignitethe arc flame, which feature has been set forth in application SerialNo. 368,193, filed in the Patent Office on March 23, 1920 by Harold F.Elliott and patented September 14, 1920, No. 1,352,883.

We claim:

1. The method of transmitting radio sign als by the aid of an arcconverter ,and a transmission circuit in such a Way that audio frequencygroups may be sent, which comprises inserting in the circuit andwithdrawing from the circuit at an audio frequency rate, an energyconsuming device, whereby the arc is extinguished and reignited at thisrate. v

2. Thel method of producing in an oscillatory circuit, current groupshaving an audio group frequency, with an arc suitable for generatingsustained alternating cur-v rents, which comprises introducing and--withdrawing resistance from said circuit at v an audio frequency rate,the value of the resistance being such that when introduced l in thecircuit, the are is extinguished.

3. A radio v telegraph signaling system comprising an arc, anoscillatory circuit conl nected to the arc, a resistance of such valuethat when introduced into the circuit the arc is extinguished, and meansfor introducing the resistance into the circuit and Withdrawing 'ittherefrom at an audio frequency rate.

4. A .radito telegraph signaling system,'

comprising an arc, an oscillatory circuit connected tol the arc, aresistance'of such value that when introduced into the circuit the arcis extinguished and a rotary make and break device adapted to introduceJthe resistance alternately extinguishing and reignitingthe varc at anaudio frequency, comprising an ener absorbin device and means forconnectin in and, disconnecting said device from t e circ-uit at anaudio frequency rate. v

In testimony whereof, We have hereunto set our hands.

HARADEN PRATT. HAROLD r. ELLro'rr. EUGENE B. rnv.

